DESIGN AND IMPLEMENTATION OF A HEATABLE, ALL-GLASS DOSER FOR SENSITIVE ORGANOMETALLIC COMPOUNDS IN AN ULTRAHIGH-VACUUM ENVIRONMENT

We report the design of an ultrahigh vacuum compatible vapor dosing sy stem for organometallic compounds. A unique feature of this doser is t he elimination of all metallic surfaces in order to reduce the reactiv ity of the organometallic molecules towards the doser walls. The vapor s only come in contact with glass, Teflon, and Kalrez and the doser is heatable to temperatures of 150 degrees C. A novel modification to a commercial glass stopcock is described. These modified valves are used in the doser to seal the ultrahigh vacuum system from the organometal lic sample compartment and have been shown to be able to allow the vac uum system to maintain ultrahigh vacuum conditions even when the sampl e compartment is vented to atmosphere. Spring-loaded Teflon seals are used to seal the valve shaft against the glass wall thereby maintainin g ultrahigh vacuum conditions and a chemically inert surface for the o rganometallic compounds. A further modification to these commercial va lves is described allowing it to function as the sample compartment fo r the organometallic material. This compartment features a heatable re servoir, vacuum seals to ultrahigh vacuum levels, and a rapid exchange design to permit the interchange of dosing materials. (C) 1995 Americ an Institute of Physics.